Desulfurization and improvement of combustion and gasification characteristics of coals

ABSTRACT

A process for the desulfurization of coal and apparatus for carrying out the process. The process includes the steps of: first, treating dry coal particles with dry chlorine gas; and, second, treating the coal particles with a purging gas. The purging gas may be, for example, dry steam or an inert gas, such as nitrogen or carbon dioxide. The apparatus includes a chlorinator means for treating the dry coal particles with dry chlorine gas and a stripper means for treating the coal particles with a purging gas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is in the field of desulfurizing and improving thecombustion and gasification characteristics of coal. Sulfur in coal is amajor source of pollutants from a coal-based energy system. The sulfurin coal appears in three main forms: pyritic, organic, and sulfate. Inorder for a coal-fired power plant to meet the various local and Federalemissions standards on sulfur dioxide (SO₂), a scrubber system presentlymust be installed. Such a system is massive and costly because it musthandle a large volume of effluent gases in order to capture the minorcomponent of pollutants. Thus, there is a major incentive to removesulfur at the feed end of a coal-fired power plant.

2. Description of the Prior Art

The prior art includes the following patents:

U.S. Pat. No. 739,374 granted to Baker et al described a process ofremoving impurities, such as iron combined with sulfur, from gold andsilver ores by contacting the ore with dry chlorine gas.

U.S. Pat. No. 1,426,054 granted to Estabrooke et al disclosed a processof desulfurizing coke by contacting the coke with chlorine gas in ablast furnace to produce volatile sulfur chloride.

U.S. Pat. No. 2,698,777 granted to Hartwick et al disclosed a process ofremoving metallic impurities from coal by contacting the coal withchlorine gas at an elevated temperature (1400° C. or higher). Themetallic impurities were converted to volatile chlorides.

U.S. Pat. No. 3,926,575 granted to Meyers disclosed a process whereinfinely divided coal containing pyrite was reacted with an aqueoussolution of sulfur dioxide and hydrochloric acid (HCl).

U.S. Pat. No. 4,054,421 granted to Robinson et al disclosed a processfor reducing the sulfur content of char by washing the char withhydrochloric acid followed by treatment with hydrogen gas.

U.S. Pat. No. 4,081,250 granted to Hsu et al described a method ofdesulfurizing coal at a moderate temperature and atmospheric pressure bythe chlorinolysis of moist coal with the assistance of an organicsolvent. In this method, chlorine gas was bubbled through a suspensionof powered moist coal in methyl chloroform at a temperature of 74° C.and atmospheric pressure for 1 to 4 hours, followed by separation,hydrolysis and thermal dechlorination of the coal.

Finally, U.S. Pat. No. 4,118,200 granted to Kruesi disclosed a processfor the desulfurization of inorganic and organic sulfur constituents ofcoal by treating the coal in a liquid fused salt bath in the presence ofchlorine to react the sulfur-containing constituents with chlorine toform chlorides and elemental sulfur. The liquid fused salt bath wascomprised of the chlorides of ferric iron, alkali metals, alkaline earthmetals, ammonia, and zinc.

SUMMARY OF THE INVENTION

The invention is a process and apparatus for the desulfurization andimprovement of combustion and gasification characteristics of dry coalparticles containing sulfur in pyritic, organic, and sulfate forms.

The inventive process comprises the steps of:

(a) treating the dry coal particles with an effective amount of drychlorine gas at a temperature and for a period of time which aresufficient for the chlorine gas to react with the sulfur in the coalparticles whereby a significant quantity of pyritic sulfur is removedfrom the coal particles; and,

(b) treating the coal particles with an effective amount of a purginggas at a temperature and for a period of time which are sufficient forthe purging gas to remove a significant quantity of organic sulfur fromthe coal particles.

The inventive apparatus comprises:

(a) a means for providing dry chlorine gas;

(b) a chlorinator means for treating said dry coal particles with anexcess amount of dry chlorine gas at a temperature and for a period oftime which are sufficient for the chlorine gas to react with the sulfurin the coal particles whereby a significant quantity of pyritic sulfuris removed from said coal particles;

(c) a means for providing a purging gas; and,

(d) a stripper means for treating said coal particles with a purging gasat a temperature and for a period of time which are sufficient for thepurging gas to remove a significant quantity of organic sulfur from saidcoal particles.

The process and apparatus have the advantages of operating at relativelylow temperatures and of removing significant amounts of pyritic sulfur,organic sulfur, and sulfate sulfur. It is highly unexpected that theprocess is capable of removing a significant amount of the organicsulfur found in coal. It is also unexpected that dry (super-heated)steam, when used as the purging gas, is capable of removingsignificantly more organic sulfur than other purging gases, such asnitrogen and carbon dioxide.

The treated coal is of a better quality for gasification and/orcombustion as a result of losing much of the original sulfur and ironvalues. Furthermore, the inventive process produces a certain degree ofporosity in the treated coal which thereby becomes more reactive thanthe original coal. Finally, no substantial calorific values of the coalare lost in the process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a small batch-type apparatus used to perform theinventive process in batches up to 600 grams of coal per run.

FIG. 2 is a flow chart illustrating a continuous-operation coaldesulfurization system or plant embodying the principles of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In general terms, the process comprises two steps. The first step is totreat the dry coal particles with dry chlorine (Cl₂) gas for a period oftime sufficient for the Cl₂ gas to react with and to remove asignificant amount of the pyritic sulfur component in the coalparticles. The coal particles may be at a temperature between 200°-700°F. (93°-371° C.) and preferably at about 450° F. (232° C.) because manytypes of coal start to devolatilize above 450° F. The Cl₂ gas may be atany operative pressure, preferably at atmospheric pressure or at aslightly higher pressure which is sufficient to fluidize the coalparticles. Higher pressures may be used, if desired, but are notnecessary. The amount of Cl₂ gas used is a function of the amount ofsulfur in the coal and is an excess of the theoretical stoichiometricamount needed.

The Cl₂ gas reacts with the pyrites (mainly iron disulfide (FeS₂)(pyrite)) in the coal to produce impure iron chlorides, for example,ferric chloride (FeCl₃), and impure sulfur chlorides, for example,sulfur monochloride (S₂ Cl₂). The impure chlorides vaporize at theoperating temperatures employed whereby a significant quantity of thepyritic sulfur component is removed from the coal in the first step.

The Cl₂ gas also reacts with or transforms, by some mechanism, theorganic sulfur component and the sulfate sulfur component present in thecoal. However, the first step alone is not effective in removing asignificant quantity of organic sulfur from the coal. The second step,described below, is required in order to remove significant amounts oforganic sulfur.

The second step is to treat the chlorinated coal particles (from thefirst step) with a purging gas, for example, dry (superheated) steam oran inert gas, such as nitrogen or carbon dioxide, for a period of timesufficient for the purging gas to remove a significant amount of theorganic sulfur component in the coal particles. The purging gas may beat a temperature of 450°-700° F. (232°-371° C.) and preferably at about500° F. (260° C.). Higher temperatures are not used because the coalwill degrade.

The purging gas may be at any operative pressure, preferably atatmospheric pressure or at a slightly higher pressure which issufficient to fluidize the coal particles. The amount of purging gasused is a function of the amount of organic sulfur in the coal and is anexcess of the theoretical amount needed to remove the organic sulfurcomponent in the coal. The purging gas also strips off and carries awayany residual Cl₂ gas and any residual chloride vapors from the firststep.

As mentioned previously, the combination of the two steps in the processis critical to the removal of organic sulfur. Furthermore, the secondstep alone (i.e., without the first step) is not effective in removing asignificant amount of sulfur of any form.

The effluent vapors may be selectively condensed by virtue oftemperature differences. The Cl₂ gas may be regenerated separately fromthe S₂ Cl₂ and FeCl₃ by known methods. Useful by-products are sulfur andiron oxide.

Referring to FIG. 1, the drawing illustrates a small batch-typeapparatus used to perform the process. Coal bed 10 (composed of dry coalparticles) is placed in column reactor 12 which is surrounded by an airgap inside outer casing 14 and which is heated by electrical heat source16. The coal bed consists of particles which are relatively small insize, preferably in the size range of 1/4"×0, that is, 1/4" in diameterdown to the smallest possible particle (powder). Most preferred areparticles in the size range of 10 mesh×100 mesh, that is, particleswhich will pass through 10 mesh, but will not pass through 100 mesh.Smaller particles become difficult to handle.

The temperature of coal bed 10 is monitored by thermocouples 18 and ismaintained at a constant temperature in the range of 200°-500° F.(93°-260° C.) at atmospheric pressure. The preferred operatingtemperature is 450° F.(232° C.).

Dry chlorine gas 20 from any convenient source (for example, acommercially available cylinder tank) is supplied to column reactor 12through control valve 22, flow meter 24, and feed line 26. The flow ofchlorine gas is upward through coal bed 10. The amount of chlorine usedis a stoichiometric excess of the amount theoretically needed to reactwith all of the sulfur in the coal particles, preferably about 4-7standard cubic feet per hour of dry chlorine gas per pound of coalparticles being treated at atmospheric pressure. Chlorine is toxic andexpensive; thus, the minimum amount possible to give a simple excess ismost preferred.

The chlorine reacts with the pyritic sulfur in the coal, producingimpure iron chlorides and sulfur chlorides which vaporize at theoperating temperatures in reactor 12. The Cl₂ gas also reacts with, orchanges in some way, the organic sulfur and sulfate sulfur in the coalparticles.

The unreacted chlorine gas, the iron chlorides, and the sulfur chloridesflow out through exit line 28 to condenser 30 containing glass beads 32.Electrical heat source 34 maintains the glass beads at a temperature lowenough to preferentially condense iron chlorides (for example, about250°-300° F. (121°-149° C.)).

The effluent then passes through effluent line 36 to water bubblercondensers 38 and 40 in ice bath 42 where sulfur and sulfur chloridesare condensed.

A typical run of Cl₂ gas is for about one hour duration. The treatmenttime may be shortened for smaller coal particle sizes or higherpressures of Cl₂ gas. After the chlorine gas has completely reacted withthe sulfur in the coal particles, control valve 22 is closed.

Purging gas 44 from any convenient source (for example, dry steam from aboiler, nitrogen from a cylinder tank, or carbon dioxide from a cylindertank) is then supplied to coal bed 10 through control valve 46, flowmeter 24, and feed line 26. The purging gas flows upwardly through coalbed 10 and strips off and carries away through effluent line 28 theorganic sulfur, any residual chlorine gas, and any residual chlorinevapors. When dry steam is used as the purging gas, it has an unexpectedbeneficial effect in loosening and removing additional increments oforganic sulfur from the coal particles.

Purging gas 44 is preferably at 450°-500° F. (232°-260° C.). Thepreferred amount of purging gas is about 8-14 standard cubic feet perhour of purging gas per pound of coal being treated at atmosphericpressure. Larger amounts may be employed, but are not necessary. Atypical run of purging gas is for about one hour duration. The treatmenttime may be shortened for smaller coal particle sizes or higher purginggas pressures.

Examples which illustrate the principles of the inventive process arepresented in Examples 1-9. The effect of temperature on thedesulfurization of Illinois #6 coal is illustrated in Examples 1 through3 whereas in Examples 4 through 6, the temperature is fixed and therelative performance of Illinois, Pittsburgh, and Washington coals isshown. Examples 7 through 9 show the effect of different purging gasconditions on the desulfurization process.

EXAMPLE 1

Bituminous coal from the Norris Mine (Central Illinois Power & LightCo.) was treated under the following two-step operating conditions in anapparatus of the type illustrated in FIG. 1:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                             200° F. (93° C.)                                 Chlorine rate: 1 SCFH (Standard                                                              ft.sup.3 per hour)                                             Amt. Coal Sample:                                                                            0.20 lb                                                        Test duration: 1 hour                                                         Coal size:     Through 10 mesh,                                                              on 80 mesh                                      (b) Purging:   Temperature:   500° F. (260° C.)                                Steam/gas rate:                                                                              Dry steam - 2 SCFH                                             Test duration: 1 hour                                          ______________________________________                                    

The results of two runs under the above operating conditions aresummarized in Table 1 below (% sulfur=% sulfur by weight in all tests):

                                      TABLE 1                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Central Illinois Power                                                                   0.64                                                                              0.50                                                                              2.28 0.45                                                                              0.51                                                                              2.11 Pyr = 29.7                                                                            No Change Negligible             & Light - Norris Mine                Sulf = -2.0*                             Bituminous Coal                      Org = 7.5                                           TOTAL S = 3.42%                                                                            TOTAL S = 3.07%                                                                            Total = 10.2                             Same coal as above                                                                       0.64                                                                              0.50                                                                              3.5  0.51                                                                              0.48                                                                              3.5  Pyr = 20.3                                                                            No Change Negligible             repeat run                           Sulf = 3.5                                                                    Org = 3.5                                           TOTAL S = 3.42%                                                                            TOTAL S =  3.19%                                                                           Total = 6.7                              __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                          *Type of sulfur increased after test.                                    

EXAMPLE 2

Bituminous coal from the Norris Mine was treated again under thefollowing two-step operating conditions in an apparatus corresponding toFIG. 1:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                             300° F. (149° C.)                                Chlorine rate: 1 SCFH                                                         Amt. Coal sample:                                                                            0.18 lb                                                        Test duration: 1 hour                                                         Coal size:     Through 10 mesh,                                                              on 80 mesh                                      (b) Purging:   Temperature:   500° F. (260° C.)                                Steam/gas rate:                                                                              Dry steam - 2 SCFH                                             Test duration: 1 hour                                          ______________________________________                                    

The results of two runs under the above operating conditions aresummarized in Table 2 below:

                                      TABLE 2                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Central Illinois Power                                                                   0.64                                                                              0.50                                                                              2.28 0.05                                                                              0.75                                                                              1.50 Pyr = 92.2                                                                            No Change Negligible             & Light - Norris Mine                Sulf = -50.0*                            Bituminous Coal                      Org = 34.2                                          TOTAL S = 3.42%                                                                            TOTAL S = 2.26%                                                                            Total = 33.9                             Same coal as above                                                                       0.64                                                                              0.50                                                                              2.28 0.04                                                                              0.85                                                                              1.65 Pyr = 93.8                                                                            No Change Negligible             repeat run                           Sulf = -70.0*                                                                 Org = 27.6                                          TOTAL S = 3.42%                                                                            TOTAL S =  2.54%                                                                           Total = 25.7                             __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                          *Type of sulfur increased after test.                                    

EXAMPLE 3

Bituminous coal from the Norris Mine was treated again under thefollowing two-step operating conditions:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                            450° F. (232° C.)                                 Chlorine rate:                                                                              1 SCFH                                                          Amt. coal sample:                                                                           0.15 lb                                                         Test duration:                                                                              1 hour                                                          Coal size:    Through 10 mesh, on                                                           80 mesh                                          (b) Purging:   Temperature:  500° F. (260° C.)                                 Steam/gas rate:                                                                             Dry steam - 2 SCFH                                              Test duration:                                                                              1 hour                                           ______________________________________                                    

The results of two runs under the above operating conditions are shownin Table 3 below:

                                      TABLE 3                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Central Illinois Power                                                                   0.64                                                                              0.50                                                                              2.28 0.01                                                                              0.45                                                                              1.35 Pyr = 98.4                                                                            No Change Negligible             & Light - Norris Mine                Sulf = 10.0                              Bituminous Coal                      Org = 40.8                                          TOTAL S = 3.42%                                                                            TOTAL S = 2.26%                                                                            Total = 47.4                             Same coal as above                                                                       0.64                                                                              0.50                                                                              2.28 0.02                                                                              0.42                                                                              1.31 Pyr = 96.9                                                                            No Change Negligible             repeat run                           Sulf = 16.0                                                                   Org = 42.5                                          TOTAL S = 3.42%                                                                            TOTAL S = 1.75%                                                                            Total = 48.8                             __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                     

EXAMPLE 4

Bituminous coal from Pittsburgh, Pennsylvania (Bureau of Mines) wastreated under the following two-step operating conditions:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                            350° F. (177° C.)                                 Chlorine rate:                                                                              1 SCFH                                                          Amt. coal sample:                                                                           0.16 lb                                                         Test duration:                                                                              1 hour                                                          Coal size:    Through 10 mesh, on                                                           80 mesh                                          (b) Purging:   Temperature:  500° (260° C.)                                    Steam/gas rate:                                                                             Dry steam - 2 SCFH                                              Test duration:                                                                              1 hour                                           ______________________________________                                    

The results of two runs under the foregoing operating conditions areshown in Table 4 below:

                                      TABLE 4                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Bureau of Mines -                                                                        2.98                                                                              0.16                                                                              0.03 0.11                                                                              0.02                                                                              0.04 Pyr = 96.3                                                                            No Change Negligible             Pittsburgh, Pa.                      Sulf = 87.5                                                                   Org = -33.3*                             Sommerset, Middle                    Total = 94.6                             Kittaning                                                                                TOTAL S = 3.17%                                                                            TOTAL S = 0.17%                                       Same coal as above -                                                                     2.98                                                                              0.16                                                                              0.03 0.15                                                                              0.01                                                                              0.05 Pyr = 95                                                                              No Change Negligible             repeat run                           Sulf = 93.8                                                                   Org = -66.6*                                                                  Total = 93.4                                        TOTAL S = 3.17%                                                                            TOTAL S = 0.21%                                       __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                          *Type of sulfur increased after test.                                    

EXAMPLE 5

Bituminous coal from the Norris Mine (Central Illinois Power & LightCo.) was treated again under the following two-step operatingconditions:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                            450° F. (232° C.)                                 Chlorine rate:                                                                              1 SCFH                                                          Amt. coal sample:                                                                           0.18 lb                                                         Test duration:                                                                              1 hour                                                          Coal size:    Through 16 mesh, on                                                           100 mesh                                         (b) Purging:   Temperature:  500° F. (260° C.)                                 Steam/gas rate:                                                                             Dry steam - 2 SCFH                                              Test duration:                                                                              1 hour                                           ______________________________________                                    

The results of two runs under the above operating conditions aresummarized in Table 5 below:

                                      TABLE 5                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Central Illinois Power                                                                   0.64                                                                              0.50                                                                              2.28 0.03                                                                              0.51                                                                              1.18 Pyr = 95.3                                                                            No Change Negligible             & Light - Norris Mine                Sulf = -2*                                                                    Org = 48.3                               Bituminous Coal                                                                          TOTAL S = 3.42%                                                                            TOTAL S = 1.78%                                                                            Total = 48.0                             Same coal as above -                                                                     0.64                                                                              0.50                                                                              2.28 0.02                                                                              0.48                                                                              1.21 Pyr = 96.9                                                                            No Change Negligible             repeat run                           Sulf = 46                                                                     Org = 46.9                                          TOTAL S = 3.42%                                                                            TOTAL S = 1.71%                                                                            Total = 50.0                             __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                          *Type of sulfur increased after test.                                    

EXAMPLE 6

Sub-bituminous coal from the State of Washington was treated under thefollowing two-step operating conditions:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                            450° F. (232° C.)                                 Chlorine rate:                                                                              1 SCFH                                                          Amt. coal sample:                                                                           0.20                                                            Test duration:                                                                              1 hour                                                          Coal size:    Through 10 mesh, on                                                           80 mesh                                          (b) Purging:   Temperature:  500° F. (260° C.)                                 Steam/gas rate:                                                                             Dry steam - 2 SCFH                                              Test duration:                                                                              1 hour                                           ______________________________________                                    

The results of two runs under the above operating conditions are shownin Table 6 below:

                                      TABLE 6                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Washington State                                                                         0.87                                                                              0.04                                                                              0.75 0.05                                                                              0.01                                                                              0.48 Pyr = 94.3                                                                            No Change Negligible             Sub-Bituminous                       Sulf = 75.0                              Mines Unknown                        Org = 36.0                                          TOTAL S = 1.66%                                                                            TOTAL S = 0.54%                                                                            Total = 67.5                             Same as above -                                                                          0.87                                                                              0.04                                                                              0.75 0.06                                                                              0.03                                                                              0.49 Pyr = 93.1                                                                            No Change Negligible             repeat run                           Sulf = 25                                                                     Org = 34.7                                          TOTAL S = 1.66%                                                                            TOTAL S = 0.58%                                                                            Total = 65.1                             __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                     

EXAMPLE 7

Lignite coal from the Noonan Mine (North Dakota) was treated under thefollowing two-step operating conditions in an apparatus of the typeillustrated in FIG. 1:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                            450° F. (232° C.)                                 Chlorine rate:                                                                              1 SCFH                                                          Amt. coal sample:                                                                           0.21                                                            Test duration:                                                                              1 hour                                                          Coal size:    Through 10 mesh,                                                              on 80 mesh                                       (b) Purging:   Temperature:  500° F. (260° C.)                                 Steam/gas rate:                                                                             Dry steam - 2 SCFH                                              Test duration:                                                                              1 hour                                           ______________________________________                                    

The results of two runs under the foregoing operating conditions aresummarized in Table 7 below:

                                      TABLE 7                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    North Dakota lignite -                                                                   0.18                                                                              0.04                                                                              0.50 0.02                                                                              0.05                                                                              0.36 Pyr = 88.9                                                                            No Change Negligible             Noonan Mine                          Sulf = -25*                                                                   Org = 28.0                                          TOTAL S = 0.72%                                                                            TOTAL S = 0.43%                                                                            Total = 40.3                             Same coal as above -                                                                     0.18                                                                              0.04                                                                              0.50 0.01                                                                              0.09                                                                              0.40 Pyr = 94.5                                                                            No Change Negligible             repeat run                           Sulf = -125*                                                                  Org = 20.0                                          TOTAL S = 0.72%                                                                            TOTAL S = 0.50%                                                                            Total = 30.6                             __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                          *Type of sulfur increased after test.                                    

EXAMPLE 8 (NITROGEN PURGING)

Bituminous coal from the Norris Mine was again treated under thefollowing two-step operating conditions:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                            450° F. (232° C.)                                 Chlorine rate:                                                                              1 SCFH                                                          Amt. coal sample:                                                                           0.18 lb                                                         Test duration:                                                                              1 hour                                                          Coal Size:    Through 10 mesh, on                                                           80 mesh                                          (b) Purging:   Temperature:  500° F. (260° C.)                                 Steam/gas rate:                                                                             N.sub.2 gas - 2 SCFH                                            Test duration:                                                                              1 hour                                           ______________________________________                                    

The results of two runs under the foregoing operating conditions aresummarized in Table 8 below:

                                      TABLE 8                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Central Illinois Power                                                                   0.64                                                                              0.50                                                                              2.28 0.03                                                                              0.78                                                                              1.47 Pyr = 95.31                                                                           No Change Negligible             & Light - Norris Mine                Sulf = -56.0*                            Bituminous Coal                      Org = 35.5                                          TOTAL S = 3.42%                                                                            TOTAL S = 2.28%                                                                            Total = 33.34                            Same coal as above -                                                                     0.64                                                                              0.50                                                                              2.28 0.04                                                                              0.82                                                                              1.68 Pyr = 93.8                                                                            No Change Negligible             repeat run                           Sulf = -64.0*                                                                 Org = 26.3                                          TOTAL S = 3.42%                                                                            TOTAL S = 2.54%                                                                            Total = 25.73                            __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                          *Type of sulfur increased after test.                                    

EXAMPLE 9 (Carbon Dioxide Purging)

Bituminous coal from the Norris Mine was again treated under thefollowing two-step operating conditions:

    ______________________________________                                        (a)  Chlorination:                                                                           Bed temperature:                                                                            450° F. (232° C.)                                 Chlorine rate:                                                                              1 SCFH                                                          Amt. coal sample:                                                                           0.18 lb                                                         Test duration:                                                                              1 hour                                                          Coal size:    Through 10 mesh, on                                                           80 mesh                                          (b) Purging:   Temperature:  500° F. (260° C.)                                 Steam/gas rate:                                                                             CO.sub.2 gas - 2 SCFH                                           Test duration:                                                                              1 hour                                           ______________________________________                                    

The results of two runs under the above operating conditions are shownin Table 9 below:

                                      TABLE 9                                     __________________________________________________________________________    LABORATORY ANALYSIS                                                                                                        (%)                                                                   Sulfur Removal                                                                        Chloride/Chlorine                Coal Sample ID                                                                           % Sulfur-Before Test                                                                       % Sulfur-After Test                                                                        Efficiency                                                                            Before                                                                             After                                                                              Btu Wt.                (Rank, County, State)                                                                    Pyritic                                                                           Sulfate                                                                           Organic                                                                            Pyritic                                                                           Sulfate                                                                           Organic                                                                            (%)     Test Test Loss                                                                              Loss               __________________________________________________________________________    Central Illinois Power                                                                   0.64                                                                              0.50                                                                              2.28 0.01                                                                              0.75                                                                              1.50 Pyr = 98.43                                                                           No Change Negligible             & Light - Norris Mine                Sulf = -50.0*                            Bituminous Coal                      Org = 34.2                                          TOTAL S = 3.42%                                                                            TOTAL S = 2.26%                                                                            Total = 33.9                             Same coal as above -                                                                     0.64                                                                              0.50                                                                              2.28 0.03                                                                              0.85                                                                              1.65 Pyr = 95.3                                                                            No Change Negligible             repeat run                           Sulf = -70.0*                                                                 Org = 27.6                                          TOTAL S = 3.42%                                                                            TOTAL S = 2.53%                                                                            Total = 26.0                             __________________________________________________________________________     S = Sulfur                                                                    Pyr = Pyritic Sulfur                                                          Sulf = Sulfate Sulfur                                                         Org = Organic Sulfur                                                          *Type of sulfur increased after test.                                    

As can be seen from Examples 1 through 3, temperature has a pronouncedeffect on sulfur removal. As the temperature was increased from 200° F.to 450° F., the sulfur removal efficiency increased steadily. 450° F.(232° C.) is believed to be an optimum, as beyond it, most coals startto devolatilize. The higher temperatures affect mostly organic sulfurremoval by severing the carbon-sulfur bonds in the coal. For ease ofreference, the average values of sulfur removal for the differenttemperatures used in Examples 1-3 are tabulated in Table 10 below:

                  TABLE 10                                                        ______________________________________                                        Operating   Sulfur Removal Efficiency                                         Temperature (Average %)                                                       (°F.)                                                                              Pyritic Organic    Sulfate                                                                             Total                                    ______________________________________                                        200 (93° C.)                                                                       25.0    5.5        0.7   8.5                                      300 (149° C.)                                                                      93.0    30.9       60.0  29.8                                     450 (232° C.)                                                                      97.6    41.7       13.0  48.1                                     ______________________________________                                    

Caking coals degrade at a lower temperature than 450° F. (232° C.). Oneof these, an eastern bituminous high-pyritic coal (Example 4), wastested at 350° F. (177° C.) instead of at 450° F. Since the coalcontained mostly pyritic-type sulfur, the process was successful inremoving most of the sulfur, even at the lower temperature.

A comparison of Examples 4 and 5 indicates that the smaller coalparticles respond better to Cl₂ treatment. However, there is a practicallimitation in generating and handling finer particles. Organic sulfur issignificantly more affected when finer particles of the coal are treatedwith chlorine. The coal from the Norris Mine, Ill., when subjected tothis process, gave the following results:

                  TABLE 11                                                        ______________________________________                                                    Sulfur Removal Efficiency                                                     (Average %)                                                       Particle Size Pyritic Organic  Sulfate Total                                  ______________________________________                                        Through 10 mesh, on                                                                         97.5    41.7     1.5     48.1                                   80 mesh                                                                       Through 16 mesh, on                                                                         96.1    47.6     no change                                                                             49.0                                   100 mesh                                                                      ______________________________________                                    

The results presented in Examples 3, 8, and 9 reveal that dry steam isbest for stripping the coal after chlorination, as it removes additionalsulfur, particularly organic sulfur.

                  TABLE 12                                                        ______________________________________                                                  Sulfur Removal Efficiency                                                     (Average %)                                                         Purging Gas Pyritic Organic    Sulfate                                                                             Total                                    ______________________________________                                        Dry steam   97.5    41.7       1.5   48.1                                     N.sub.2     94.6    30.9       60.0  28.5                                     CO.sub.2    96.9    30.9       60.0  30.0                                     ______________________________________                                    

As noted before, an eastern bituminous high-pyritic coal (Example 4) hadthe greatest overall sulfur removal efficiency, even at lowertemperatures. The average values of sulfur removed for the differentcoals used in Examples 3, 4, 6 and 7 are tabulated in Table 13 below:

                  TABLE 13                                                        ______________________________________                                                   Sulfur Removal Efficiency                                                     (Average %)                                                        Coal Rank    Pyritic Organic   Sulfate Total                                  ______________________________________                                        Midwestern Bitumin-                                                                        97.5     41.75     1.5    48.1                                   ous (Illinois #6)                                                             Eastern Bituminous                                                                         95.7    no change 90.7    94.5                                   (Pittsburgh)                                                                  (Run at lower temp.)                                                          Sub-Bituminous                                                                             93.7    35.4      62.5    66.7                                   (Washington State)                                                            Lignite      91.7    24.0      no change                                                                             35.5                                   (North Dakota)                                                                ______________________________________                                    

Referring to FIG. 2, the drawing is a flow chart which illustrates acontinuous operation coal desulfurization system or plant. Coal pile 48is run-of-mine dry coal having a size range of 31/2"×0. The coal isstored in coal bin 50 from which it is transferred by feeder 52 toBar-Grizzly screen 54 and then to secondary crusher 56. Crusher 56 sizesthe feed coal in the size range of 1/4"×0 for chlorinator reactor 58.

The coal particle size depends on the manner in which the pyritic sulfuroccurs in the coal. With respect to organic sulfur, particle size doesnot make any difference directly, but the coal particle size mayindirectly affect desulfurization rates.

Chlorinator 58, preferably a spouted bed chlorinator, operates at atemperature level of about 470°-700° F. (232°-371° C.) with excesschlorine gas. Coal of 1/4"×0 size is continuously fed into chlorinator58 where coal bed 59 is maintained, preferably in a fluidized state.

A spouted bed chlorinator has the structure and mode of operation of theapparatus shown in my copending U.S. patent application Ser. No. 183,781filed Sept. 3, 1980 entitled "Apparatus For Mixing And DistributingSolid Particulate Material," and the disclosure of that application isincorporated by reference herein.

Vapors from chlorinator 58 pass to iron chloride separator-cooler 60where iron chlorides are condensed and removed. Vapors fromseparator-cooler 60 then pass to sulfur and monochloride condenser 62where sulfur, sulfur monochloride, and other gases (except chlorine) arecondensed and removed.

Coal from chlorinator 58 is transferred continuously to stripper 64where a purging gas (for example, dry steam or an inert gas, such ascarbon dioxide or nitrogen) at a temperature level of about 450°-700° F.(232°-371° C.) is blown upwardly through coal bed 65 to eliminateorganic sulfur. Preferably, stripper 64 is a fluid bed stripper whereincoal bed 65 is maintained in a fluidized state.

Iron chloride separator-cooler 60 operates at a constant temperature ofabout 250° F. (121° C.) The unit contains some sodium chloride (NaCl) tocapture ferrous chloride vapor as an impurity which has a highercondensing temperature. NaCl is also needed in batch chlorine generator66 for the generation of Cl₂ from ferric chloride.

Sulfur and monochloride condenser 62, where most of the sulfurmonochloride and other impurities are condensed, operates at the ambienttemperature or below. Free chlorine gas passes to mixer 68, then throughcooler 70 to remove any moisture. From time to time, sulfur and otherimpurities have to be cleaned out of condenser 62.

Mixer 68 may be a simple tee connection. It receives chlorine from bothcondenser 62 and batch chlorine generator 66.

The dry chlorine from cooler 70 is stored in chlorine storage tank 72after passing through compressor 74. The chlorine is fed by pump 75 tospouted bed chlorinator 58 from storage tank 72.

The removal of organic sulfur, residual Cl₂ gas, residual ironchlorides, and sulfur from the surface of the coal particles in coal bed65 (inside stripper 64) is accomplished by means of the purging gaspreviously discussed. The chlorinator and stripper may be combined tooperate in a single unit (for example, as in FIG. 1). From stripper 64,the prepared coal is then transferred to a storage receptacle where itis ready for gasification or combustion processing.

From time to time, sodium and iron chlorides, and carbon particles withother combustibles are removed from iron chloride separator-cooler 60and transferred to batch chlorine generator 66. Extra coke and oxygenare needed to generate chlorine and iron oxide. This batch generator isoperated intermittently and also produces iron oxide, a useful productfrom the wastes.

The above-described embodiments are intended to be illustrative, notrestrictive. The full scope of the invention is defined by the claims,and any and all equivalents are intended to be embraced.

I claim:
 1. A process for the desulfurization and improvement ofcombustion and gasification characteristics of dry coal particlescontaining sulfur in pyritic, organic, and sulfate forms, said processcomprising the steps of:(a) treating said dry coal particles with aneffective amount of dry chlorine gas at a temperature and for a periodof time which are sufficient for the chlorine gas to react with thesulfur in the coal particles whereby a significant quantity of pyriticsulfur is removed from the coal particles; and, (b) treating the coalparticles with an effective amount of a purging gas at a temperature andfor a period of time which are sufficient for the purging gas to removea significant quantity of organic sulfur from the coal particles.
 2. Theprocess defined in claim 1 wherein the coal particles are in the sizerange of 1/4"×0.
 3. The process defined in claim 1 wherein the coalparticles are in the size range of 10 mesh×100 mesh.
 4. The processdefined in claim 1 wherein the amount of chlorine gas used is astoichiometric excess of the amount theoretically needed to react withall of the sulfur in the coal particles.
 5. The process defined in claim1 wherein about 4-7 standard cubic feet per hour of dry chlorine gas isused per pound of coal particles being treated.
 6. The process definedin claim 1 wherein the dry chlorine gas is at atmospheric pressure andat a temperature of about 200°-700° F.
 7. The process defined in claim 1wherein the dry chlorine gas is at a temperature of about 450° F.
 8. Theprocess defined in claim 1 wherein the coal particles are treated withdry chlorine gas for a period of about one hour.
 9. The process definedin claim 1 wherein the purging gas is selected from the group consistingof dry steam, nitrogen, and carbon dioxide.
 10. The process defined inclaim 1 wherein the purging gas is dry steam.
 11. The process defined inclaim 1 wherein about 8-14 standard cubic feed per hour of the purginggas is used per pound of coal particles being treated.
 12. The processdefined in claim 1 wherein the purging gas is at atmospheric pressureand at a temperature of about 450°-700° F.
 13. The process defined inclaim 1 wherein the purging gas is at a temperature of about 500° F. 14.Apparatus for the desulfurization and improvement of combustion andgasification characteristics of dry coal particles containing sulfur inpyritic, organic, and sulfate forms, said apparatus comprising:(a) ameans for providing dry chlorine gas; (b) a chlorinator means fortreating said dry coal particles with an excess amount of dry chlorinegas at a temperature and for a period of time which are sufficient forthe chlorine gas to react with the sulfur in the coal particles wherebya significant quantity of pyritic sulfur is removed from said coalparticles; (c) a means for providing a purging gas; and, (d) a strippermeans for treating said coal particles with a purging gas at atemperature and for a period of time which are sufficient for thepurging gas to remove a significant quantity of organic sulfur from saidcoal particles.
 15. The apparatus defined in claim 14 wherein thechlorinator means and the stripper means are combined in a single unit.16. The appartus defined in claim 14 wherein the chlorinator means is aspouted bed chlorinator.
 17. The apparatus defined in claim 14 whereinthe stripper means is a fluid bed stripper.
 18. A system for thedesulfurization and improvement of combustion and gasificationcharacteristics of dry coal particles containing sulfur in pyritic,organic, and sulfate forms, said system comprising:(a) a coal storagemeans for storing said dry coal particles; (b) a coal feeder means forfeeding said coal particles from said coal storage means; (c) a coalcrusher means for crushing and reducing the size of said coal particlesreceived from said coal feeder means; (d) a means for providing drychlorine gas; (e) a chlorinator means for treating said coal particleswith an excess amount of dry chlorine gas whereby a significant quantityof pyritic sulfur is removed from said coal particles; (f) a means forproviding a purging gas; (g) a stripper means for treating said coalparticles from said chlorinator means with a purging gas whereby asignificant quantity of organic sulfur is removed from said coalparticles; (h) an iron chloride separator means for removing ironchlorides from vapors received from said chlorinator means and from saidstripper means; and, (i) a sulfur and monochloride condenser means forremoving sulfur and sulfur monochloride from vapors received from saidiron chloride separator means.
 19. The apparatus defined in claim 18wherein the chlorinator means is a spouted bed chlorinator.
 20. Theapparatus defined in claim 18 wherein the stripper means is a fluid bedstripper.